Chapter 5 - Features of regional Indian monsoon rainfall extremes

Abstract

The Indian subcontinent is home to 1.39 billion people, mainly dependent on the agrarian-based economy. The Indian summer monsoon rainfall from June to September plays a vital role in providing water for agricultural and other lively needs. This rainfall is highly varying in the spatiotemporal domain and thus, leads to localized and organized extreme events in the form of floods on micro to mesoscale. The extreme rainfall events aggravate developing countries like India since the country's 54.6% human resources are involved in agriculture and allied sectors. Thus, understanding the characteristics of extreme events throughout India is important for the country's overall development. This chapter explores the systematic evolution of the studies of the extreme rainfall events over the Indian subcontinent and the regional characteristics. The linear trends reported by various studies are also explored and found that the trends are nonuniform throughout the nation. The nature and frequency of occurrence of these events are showing regional features. Therefore, the focus is on the extreme events in Peninsular India, central India, northeast regions, and the Himalayan regions. The dynamics of extreme events in all these regions are different. In general, Himalayan areas are controlled by extratropical intrusion and low-pressure systems. However, in the northeast regions, the main dynamic reason is the westerly regimes of the southerly wind and synoptic systems from the nearby oceans. Central India is governed by varying mechanisms from oceanic warming to topographical features. However, Peninsular India received its extremes in two seasons. The Tamil Nadu region experiences it in the northeast monsoon season, and the windward side of the Western Ghats experiences it during the southwest monsoon period. Hence, both areas have different attributing mechanisms. Additionally, the chapter investigates the future projections of the extreme events.